The overall objectives of the total project are to investigate in some detail the nature of host-virus interactions and the relationship of other host factors to the development of bronchial hyperreactivity and reversible reactive airway disease (RAD) in early childhood. Studies have been initiated to examine the specific immunologic mechanisms in the respiratory tract and the possible role of common respiratory viral infections and virus specific immune responses in the etiology and pathogenesis of reactive airway disease in infancy and childhood. The specific aims set forth for the entire project period as outlined in the original application included a) examination of the spectrum of viral infections in the respiratory tract, the nature of infection-induced immune response and the possible relationship to the development of infection associated RAD, b) investigation of the role of bronchiolitis in infancy in the development of bronchial asthma in later life, c) role of common viral infection of the respiratory tract in provoking bronchial hyperreactivity in established cases of bronchial asthma, and d) establishment of experimental animal model to study the mechanisms of virus induced reactive airway disease.